Method and apparatus for production of bulked yarn



D. STARKIE 3,166,822

METHOD AND APPARATUS FOR PRODUCTION OF BULKED YARN Jan. 26, 1965 FiledApril 11, 1961 United States Patent Ofifice $366,822 Patented Jan. 26,1965 Co-pending patent application No. 7 26,928, filed April 7, 1958,describes a method and apparatus for processing thermoplastic yarns togive them stretch properties by impart-ing a crimp thereto. The methodin essentials comprises stretching a thermoplastic filament, heating itWhile stretched in such a manner that a temperature gradient is set upacross the filament, cooling it and permitting it to relax. Morespecifici-ally a thermoplastic yarn consisting of a single filament or aplurality of filaments is first stretched by at least 10% in length bypassing it progressively around grooves formed in the peripheries of aconical stretching roller (which is driven) and a conical jockey pulley.The yarn while being maintained in its stretched condition is thenpassed through the nip between two plain rollers relatively biassedtogether. One of these rollers is heated and is power driven and theother is cooled and is driven by cont-act with the yarn which it nipsagainst the hot roller. Since the yarn is nipped between the hot andcold rollers it is prevented from rotating about its own axis and atemperature gradient is established across its cross-section. From thenip between the hot and cold rollers the yarn, still in its stretchedcondition, passes round a final grooved cylindrical take-oft roller, anda grooved jockey pulley, from which it is delivered ready to be Woundinto a package. In passing round these last mentioned rollers and ondelivery by them the yarn cools, and on delivery by them relaxes, and itthen possesses a helical crimp. This crimp can be further developed bysubmitting the yarn to a further heat treatment either before or afterit has been made into fabric. Such further heat treatment shrinks theyarn and tightens up the helix.

Such yarn, either in single filament or plural filament form, isexcellent for the construction of stockings and like articles offootwear having a very pronounced capacity for being stretched. Forexample when such a yarn is knitted into a womans stockings and as partof the finishing process the stockings are subsequently heated whileimmersed in a liquid, a latent capacity for additional crimp is fullydeveloped and the fabric of the stockings contracts to a fraction of itsoriginal knitted size. Such stockings are highly extensible, recoverrapidly from distortion and stretching and by reason of these propertiesgive cling and accurate fitting to the contours of the legs of thewearers however varied those contours may be.

However yarns made in this way are not entirely suitable for otherpurposes such as for example as the manufacture of underwear andouterwear and some half-hose where bulk and flufiiness are moreimportant than high extensibility and rapid recovery. Plural filamentyarns made in accordance with the method described exhibit a tendencyfor the coils in the individual filaments to remain in phase and whilethis gives sheerness and elasticity to the resultant fabric theseproperties, although desirable in the case of womens stockings, are notof primary value in the other garments mentioned above in which softnessof handle and good heat insulation by virtue of the trapping of airpockets in the fabric are important desiderata.

It has now been found that yarn processed according to the aforesaidpatent application can be given a softer handle and improved heatinsulating properties if at least some of the latent crimp is developedby heating the yarn under substantially no tension and allowing it tocontract by a predetermined amount before it is knitted into fabric.

The invention therefore provides a method of bulking a plural-filamentyarn consisting of a plurality of thermoplastic filaments that have beensubjected to a crimping treatment, which comprises traversing the yarnthrough a zone in which it is permitted to contract lengthwise to apredetermined extent while subjecting it to substantially uniformheating.

. ient means.

The invention further provides a method of bulking a plural-filamentyarn consisting of a plurality of thermoplastic filaments that have beensubjected to a crimping treatment, which comprises forwarding the yarnat a predetermined input speed to the periphery of a roller whichrotates at a higher peripheral speed than the input speed and tends tospeed up the yarn, passing the yarn through a zone in which it ispermitted to contract lengthwise to a predetermined extent whilesubjecting it to substantially uniform heating, and delivering the yarn,by a let-off device, at a linear speed less than the input speed.

This bulking may be carried out immediately after the yarn has beentreated in accordance with the aforesaid co-pending application so thatthe two form a continuous process. Alternatively the bulking can becarried out as a separate operation.

This invention further includes apparatus for bulking a plural-filamentyarn consisting of a plurality of thermoplastic filaments that have beensubjected to a crimping treatment, which apparatus is constructed andarranged to permit lengthwise contraction of the running yarn to apredetermined extent while subjecting it to substantially uniformheating and comprises yarn input means for passing the yarn into theapparatus at a predetermined speed, let-off means for delivering theyarn from the apparatus at a less linear speed than the input speed, andheating means for subjecting the yarn to substantially uniform heatingwhile running between said input and let-01f means. The heating means ispreferably a yarn engaging roller, drum, or the like.

The foregoing and other features of the invention set out in theappended claims are incorporated in the method and apparatus which willnow be described with reference to the accompanying drawing which islargely diagrammatic and in which FIGURE 1 is a side elevation andFIGURE 2 a front elevation of the bulking apparatus.

The plural yarn is delivered from the roller 2 (which is the groovedlet-off roller 14 of the co-pending patent application) at apredetermined input speed. It then passes over a small arc of theperiphery of a smooth roller 3 or the like which is driven to rotate ata higher peripheral speed than the input speed. Roller 3 therefore tendsto speed up the yarn and its purpose is to prevent the yarn in itsrelaxed condition from wrapping back on the roller 2. It exerts a slightscrubbing action on the yarn, which may tend to shift the convolutionsof the yarn out-of-phase. It has been found advantageous to give theperiphery of roller 3 a fine satin finish by fine sand blasting followedby light polishing. This reduces the area of contact of the yarn withthe roller and avoids the yarn sticking to the roller. The yarn isfinally delivered through the nip between smooth let-off rollers 4, 5.Roller 4 is power driven and roller 5 is free running and the tworollers are biassed together by an air piston, spring, weight loading,or any other conven- The peripheral speed of rollers 4 and 5 is slowerthan that of roller 2 by a predetermined amount. 30% slower has beenfound to be suitable but other amounts depending on the characteristicsrequired in the final yarn can be used.

The fact that yarn is forwarded into the apparatus by roller 2 at alinear speed greater than that at which it is delivered from theapparatus by let-off rollers 4, would normally cause a surplus of yarnto be built up within the apparatus. However after leaving roller 3 theyarn is heated substantially uniformly. It therefore contracts to anextent (30%) governed by the speed difference just mentioned. The effectof the heating is to develop the latent crimp in the yarn so that thelatter remains taut in its passage through the apparatus. The individualfilaments are not allowed to take up their helical form but assume asimple wave form which is close to a sine wave. The helical formationwhich would tend to pull the individual filaments into phase is absentand the wavy filaments are able to separate somewhat, giving the yarn abulky, fluffy, character.

The substantially uniform heating is preferably achieved by passing theyarn, between roller 3 and rollers 4, 5, over a considerable arc of theperiphery of a large roller 6, within a deep groove 6' therein, thisroller 6 being maintained at a substantially constant elevatedtemperature. The use of a deep groove ensures that the yarn is heateduniformly during its passage over roller 6 and also ensures that it isprotected from draughts. The peripheral speed of the bottom of groove 6'in roller 6 is arranged to be the same as the peripheral speeds ofrollers 4 and 5.

It will be appreciated that the temperature at which roller 6 must bemaintained in order to heat the yarn up to the temperature required tocause crimp development will be governed by the conditions ofprocessing: obviously the speed at which the yarn travels and the lengthof the arc of contact which the yarn makes with roller 6 are importantfactors. It has been found that with roller 2 delivering yarn at therate of 200 yards per minute and the arc of contact of the yarn with theroller 6 being approximately 6" (being about one quarter of the rollercircumference), the temperature of roller 6 should be a little above themelting point of the material of the yarn being processed.

There are a number of ways in which roller 6 can be heated, for exampleit can be constructed as a hollow shell rotating around a stationaryelectric heating element. The heating element may be carried by astationary hollow shaft through which its leads extend. The roller 6 maybe supported on this hollow shaft or on a rotating shaft, for example ona hollow rotating shaft housing the stationary shaft.

After emerging from the nip between roller-s 4, 5 the yarn is wound ontoa package in known manner, a downtwister being suitable. Thedown-twister will apply sufficient tens-ion to the yarn to straightenout the developed crimps in the filaments and these will subsequentlyreappear when :the yarn is allowed to hang slack and after a subsequentrelaxing treatment.

Since roller 6 must be held at an elevated temperature, it is notpossible to thread up the equipment and to permit the yarn to remainstationary and in contact with the roller while the latter is beingheated up. it is therefore convenient to heat up the roller and to holdthe threaded-up yarn out of contact with it until the apparatus isbrought into operation. For this purpose means are provided for engagingthe yarn between rollers 3 and rollers 4 and 5 and for holding the yarnout of contact with roller 6. In the illustrated construction there is afree running grooved pulley 8 on the end of an arm 7 pivoted at 9.Before starting the run, roller 6 is brought to its correct temperatureand the arm 7 with its pulley 8 are in the position shown in dottedlines in FIG. 1. It will be seen that the yarn, also shown in dottedlines, extends over the displaced pulley 8 and is withheld from contactwith roller e. The arm '7 may then be moved to the right in FIG. 1 intoits full line position so that it carries the yarn into the groove 6' inroller 6 and roller 8 passes out of contact with the yarn.

When commencing processing operations in accordance with patentapplication No. 726,928 and the present invention, roller 6 is alreadyhot as is also roller 13 of said application. Arm 7 is in the dottedline position and the nip rollers 4 and 5 are open. Cold roller 26 ofsaid application is moved to nip the yarn with hard pressure against thehot roller 13. The running yarn treated in accordance with the saidapplication is delivered by roller 2 into the present apparatus andafter passing over fas -running roller 3 and the displaced pulley 8,without making contact with hot roller 6, travels down through an opengap between rollers t and 5. Arm 7 is then swung to its full lineposition so that the yarn is carried into the groove of roller 6, andthe nip between rollers i and 5 is closed. Therefore the yarn emergingfrom between rollers 4 and 5 is fully processed and may be wound onto asuitable package.

The displaceable arm 7 permits the apparatus of the present invention tobe brought into and out of operation as required and therefore permit-sstretch yarn produced according to the said co-pending application topass through the present apparatus without further treatment or to bebLlllfBCl in the present apparatus as required. Preferably when the arm7 is displaced to its dotted line position the rollers 4 and 5 areopened, and they are closed when it is brought to its full lineposition. Appropriate connections are provided between arm 7 and rollers4 and 5, to produce the movements just referred to. The arm may bemoved, and the rollers opened or closed, manually. Any suitable meansfor driving 2, 3, 4, and 6 from a power source may be provided.

The present invention is applicable, not only to stretch yarn producedaccording to patent application No. 726,928 but also to stretch yarnsproduced by other processes especially those produced by twistinguntwisting.

What I claim is:

l. A method of bulking a previously only partially crimpedplural-filament thermoplastic yarn which comprises feeding the yarn at apredetermined input speed, forwarding said yarn at an increased speedprior to entrance into and through a treating zone, decreasing the speedof the yarn in said zone to substantially completely untension said yarnand subjecting said yarn to substantially uniform heating in thesubstantially completely untensioned condition thereof resulting inlengthwise contraction of said yarn to a predetermined extent as saidyarn passes out of said zone at the same decreased speed, and deliveringsaid yarn at a predetermined exit speed which is substantially equal tothe decreased speed of said yarn in said zone.

2. A method according to claim 1 in which the forwarding speed isgreater than the exiting speed and the amount of lengthwise contractionof the yarn is about 30% depending on the difference between theforwarding speed and the exiting speed.

3. Apparatus for bulking a previously treated pluralfilarnentthermoplastic yarn in which the tendency to crimp is developed by theestablishment of a heat gradient across the yarn, which comprises meansfor feeding the yarn under sufficient tension to suppress the crimps andat a predetermined input speed into a treating zone including means forforwarding said yarn at an increased speed into said treating zone,means for decreasing the speed of said yarn to such an extent that saidyarn is in the substantially completely untensioned condition and fortreating substantially uniformly said yarn with heat within said zone sothat a predetermined amount of lengthwise con-traction occurs on thepart of said yarn while in the substantially completely untensionedcondition thereof whereby a bulking effect is achieved by producing ashrinkage in the yarn along the side exposed to the relatively coolertemperature while leaving sub- 5 stantially unaffected the side exposedto the relatively hotter temperatures of the gradient, and means forwithdrawing said contracted yarn substantially at the same decreasedspeed.

4. Apparatus according to claim 3, wherein said means forwarding saidyarn at an increased speed includes a roller having a fine satin finish.

5. Apparatus according to claim 4, further comprising means forselectively holding said yarn, while threaded in said apparatus, out ofcontact with the means for treating the yarn with heat.

6. Apparatus according to claim 3, further comprising means forselectively holding said yarn, while threaded in said apparatus, out ofcontact with the means for treating the yarn with heat.

7. A method of bulking a plural filament yarn to which there has beenapplied a crimping treatment in which the travelling plural-filamentyarn is stretched to a predetermined extent, its filaments heated on oneside while in the stretched condition to establish a temperaturegradient across each filament between relatively hot and relatively coolsides thereof, and thereupon is cooled, whereby the relatively hot sideretains a greater proportion of the applied elongation than does therelatively cool side and each filament assumes a crimpled formation,comprising the steps of:

traversing the thus-crimped yarn in the substantially completelyuntensioned condition thereof through a zone in which the relativelycool side of the yarn is shrunk bysubjecting the yarn to substantiallyuniform heating thereby accentuating the crimped formation,

and thereafter cooling said yarn whereby the accentuated crimp formationis confirmed in said yarn.

8. A method of bulking a plural filament yarn to which there has beenapplied a crimping treatment in which the travelling plural-filamentyarn 'is stretched to a predetermined extent, its filaments heated onone side while in the stretched condition to establish a temperaturegradient across each filament between relatively hot and relatively coolsides thereof, and thereupon is cooled, whereby the relatively hot sideretains a greater proportion of the applied elongation than does therelatively cool side and each filament assumes a crimped formation,comprising the steps of:

traversing the thus-crimped yarn in the substantially completelyuntensioned condition thereof through a zone in which the relativelycool side of the yarn is shrunk by subjecting the yarn to substantiallyuni form heating at such temperature as to leave substantiallyunaffected the pre-set elongation in the relatively hot side of the yarnthereby accentuating the crimped formation,

and thereafter cooling said yarn whereby the accentuated crimp formationis confirmed in said yarn. 9. A method for accentuating the crimp in acrimped yarn in which the crimp is only partially developed, and inwhich the partially developed crimp is the result of a temperaturegradient established across each filament in the tensioned conditionthereof so that the relatively hot side retains a greater proportion ofthe applied elongation than the relatively cool side, thereby resultingin a crimped formation, comprising the steps of:

feeding the yarn at a first linear speed; thereafter heating said yarnwithin a treating zone in the substantially completely untensionedcondition thereof while travelling at a reduced linear speed to enableshrinkage of the relatively cool side and therewith accentuate the crimpdevelopment thereof;

and delivering the thus-treated yarn at a linear speed substantiallyequal to the linear speed within said treating zone.

10. A method of bulking a plural filament yarn to which there has beenapplied a crimping treatment in which the travelling plural-filamentyarn is stretched to a predetermined extent, its filaments heated on oneside while in the stretched condition to establish a temperaturegradient across each filament between relatively hot and relatively coolsides thereof, and thereupon cooled, whereby the relatively hot sideretains a greater proportion of the applied elongation than does therelatively cool side and each filament assumes a crimped formation,comprising the steps or": V

feeding the yarn at a predetermined linear input speed;

forwarding said yarn at an increased linear speed prior to entrance intoa treating zone;

decreasing the speed of the yarn and treating the same with heat withinsaid treating zone to thereby enable shrinkage, in the substantiallycompletely untensioned condition of said yarn, of the relatively coolside of the filament thereby. accentuating the crimped formation;

and thereafter cooling said yarn during delivery thereof at a linearspeed substantially equal to the linear speed thereof within saidtreating zone to thereby confirm the accentuated crimp formation withinsaid yarn.

11. A method of bulking a yarn comprised of a plurality ofthermo-plastic filaments having a crimped configuration, the crimpedconfiguration of each individual filament being substantially in phasewith adjacent filaments, characterized by feeding the yarn to a treatingzone,

subjecting said yarn in the treating zone to a scrubbing action to shiftthe individual filaments relative to each other, heating said yarn undersubstantially tensionless conditions to obtain a lengthwise contractionthereof, and withdrawing the contracted yarn from said treating zone.

12. A method of bulking yarn comprised of a plurality of thermo-plasticfilaments having a crimped configuration produced by a temperaturegradient set up thereacross, the crimped configuration of eachindividual filament being substantially in phase with adjacentfilaments, characterized by feeding the yarn to a treating zone,

contacing said yarn in the treating zone with a roller operating at agreater speed than the input speed of the yarn to the treating zonewhereby the individual filaments are shifted relative to each other,

heating said yarn under substantially tensionless conditions to obtain alengthwise contraction thereof, and

withdrawing the contracted yarn from said treating zone.

13. Apparatus according to claim 3, wherein the plural-filamentthermoplastic yarn is delivered to said feeding means immediatelyfollowing the crimping treat ment.

14. A method of bulking a plural-filament thermoplastic yarn, which hasbeen previously treated to impart thereto a permanent tendency to crimp,which comprises feeding the previously crimp-treated yarn to a treatingzone in such tensioned condition as to prevent the formation of thecrimps that would otherwise form, subjecting said yarn in asubstantially untensioned condition thereof within said treating zone toa substantially uniform heating before in phase crimps can form in theuntensioned yarn thereby resulting in out-of-phase formation of thecrimps, and delivering the thus bulked yarn with the out-of-phase crimpsthereof.

15. A method of bulking a plural-filament thermoplastic yarn, which hasbeen previously treated to impart thereto a permanent tendency to crimp,which comprises:

feeding the previously crimp-treated yarn to a treating zone at a firstspeed and in such tensioned condition as to prevent the formation of thecrimps that would otherwise form, subjecting said yarn in asubstantially untensioncd condition thereof within said'trcating zoneto' a substantially uniform heating before in phase crimps can form inthe untensioned yarn thereby resulting in out-of-phase formation of thecrirnps, and delivering the thus bullied yarn with the out-of-phasecrimps thereof at a second speed which is less than said first speed byan amount substantially proportional to the lengthwise contraction ofthe yarn in the treating zone.

16. A method of producing in a continuous process a bulked yarn from atravelling plural filament thermoplastic yarn, wherein the travellingplural filament yarn is first subjected to a crimping treatment bystretching it, as it travels, to a predetermined extent and renderingpermanent a greater proportion of the stretch at one side of eachfilament than at the other side by establishing a temperature gradientacross each filament between a relatively hot and a relatively cool sidethereof, whereby the relatively hot side retains a greater proportion ofthe applied elongation than does the relatively cool side, and eachfilament tends to assume a helically-crimped formation, comprising thesteps of immediately following said treatment accentuating'the lengthdifference between the two sides of each filament of the travelling yarnand imparting to the yarn an enhanced bulk by shrinking the relativelycool side of each filament by traversing the still-travelling yarn,under substantially no tension, through a zone in which it is heateduniformly.

17. A method according to claim 16, wherein immediately following thesaid treatment, the travelling yarn is brought into contact with thesurface of a, roller travelling at a higher speed than the yarn.

18. Apparatus for bulking a previously treated pluralfilamentthermoplastic yarn in which the tendency to crimp is developed by theestablishment of a heat gradient across the yarn, which comprises meansfor feeding the yarn under sufiicient tension to suppress the crinipsand at a predetermined input seeed into a treating zone including meansfor forwarding said yarn at an increased speed into said treating zone,means for decreasing the speed of said yarn to such an extent that saidyarn is in the substantially completely untensioned condition and fortreating substantially uniformly said yarn Within said heating zone sothat a predetermined amount of lengthwise contraction occurs on the partof said yarn While in the substantially completely untensioned conditionthereof whereby a bulking effec is achieved by producing a shrinkage inthe yarn along the side exposed to the relatively cooler temperaturewhile leaving substantially un affected the side exposed to therelatively hotter ten1pera tures of the gradient, and means forwithdrawing said contracted yarn substantially at the same decreasedspeed, the means for treating the yarn with heat including a rollerhaving a deep groove to ensure uniform heat ng of the yarn and crotciion thereof from draughts.

19. Apparatus according to claim 18 wherein said means forwarding saidyarn at an increased speed includes a roller having a line satin finish.

References Cited by the Examiner UNITED STATES PATENTS 2,377,310 6/45Robbins 2872 2,673,546 3/54 Newton 28-451 2,952,033 9/60 Goodwin.2,977,746 4/61 Klein et al. 5734 3,020,621 2/62 Sacks 287l.3

FOREIGN PATENTS 219,270 5/58 Australia. 203,619 5/ 59 Austria.

MERVIN STEIN, Primary Examiner.

3. APPARATUS FOR BULKING A PREVIOUSLY TREATED PLURALFILAMENTTHERMOPLASTIC YARN IN WHICH THE TENDENCY TO CRIMP IS DEVELOPED BY THEESTABLISHMENT OF A HEAT GRADIENT ACROSS THE YARN, WHICH COMPRISES MEANSFOR FEEDING THE YARN UNDER SUFFICIENT TENSION TO SUPPRESS THE CRIMPS ANDAT A PREDETERMINED INPUT SPEED INTO A TREATING ZONE INCLUDING MEANS FORFORWARDING SAID YARN AT AN INCREASED SPEED INTO SAID TREATING ZONE,MEANS FOR DECREASING THE SPEED OF SAID YARN TO SUCH AN EXTENT THAT SAIDYARN IS IN THE SUBSTANTIALLY COMPLETELY UNTENSIONED CONDITION AND FORTREATING SUBSTANTIALLY UNIFORMLY SAID YARN WITH HEAT WITHIN SAID ZONE SOTHAT A PREDETERMINED AMOUNT OF LENGTHWISE CONTRACTION OCCURS ON THE PARTOF SAID YARN WHILE IN THE SUBSTANTIALLY COMPLETELY UNTENSIONED CONDITIONTHEREOF WHEREBY A BULKING EFFECT IS ACHIEVED BY PRODUCING A SHRINKAGE INTHE YARN ALONG THE SIDE EXPOSED TO THE RELATIVELY COOLER TEMPERATUREWHILE LEAVING SUBSTANTIALLY UNAFFECTED THE SIDE EXPOSED TO THERELATIVELY HOTTER TEMPERATURES OF THE GRADIENT, AND MEANS FORWITHDRAWING SAID CONTRACTED YARN SUBSTANTIALLY AT THE SAME DECREASEDSPEED.